From: dblack@...
Date: 2002-10-22T08:44:18+09:00
Subject: Re: functional Ruby equiv to this perl snippet

Hi --

On Tue, 22 Oct 2002, Bob X wrote:

> "Daniel Berger" <djberge@qwest.com> wrote in message
> news:3DB473B8.9454B953@qwest.com...
> <snip>
>  >
> > > You can do something very similar in Ruby, using "fail" instead of
> "die".
> > > For example:
> > >
> > >         def open_file name
> > >           f = File.open(name) or fail "couldn't open #{name}"
> > >           return f
> > >         end
> > >
> > > --Mirian
> >
> > Note that this isn't strictly necessary, unless you just want to provide
> your
> > own error message.  Ruby will die at that point anyway if the file doesn't
> > exist (and tell you why).  No need to test.
> >
> > f = File.open("blah")
> > # Results in this:
> > # in `open': No such file or directory - "blah" (Errno::ENOENT)
> >
> > Regards,
> >
> > Dan
> >
> I would want to provide my own error message. I did not see the "fail"
> option...grrrrr.

"or fail" won't work the way "or die" does in Perl; you need to
rescue, because you're catching an exception (not just branching on a
false return value).  Something like:

  f = File.open("blah") rescue fail "That did not work"


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav